This invention relates generally to a method for controlling an input clutch of a manual transmission on the basis of direct, real-time torque measurements inside the transmission or in a vehicle driveline.
The market share of vehicles equipped with manual transmissions remains low in this country partly due to operating complexity involved in the gear shifting process. A typical manual transmission system requires a coordinated use of feet to operate the transmission input clutch and throttle pedals while moving a shift fork through a hand-operated shift lever. It also requires a foot-based control to slip the clutch for driving a vehicle at a low speed.
Missed clutch release timing, poor clutch slip control or missed engagement timing results in a stalled engine or undesirable noise, vibration and harshness (NVH) such as clutch shudder.
A robotized manual transmission system with electronically-controlled input clutch has been in use for limited production applications. Its clutch control primarily relies on clutch actuator position and slip speed measurements during clutch release, slip and engagement processes. However, these measurements cannot be directly utilized to accurately compute torque transmitted through the slipping input clutch. More specifically, there is no reliable method to accurately estimate clutch torque based on clutch actuator position and slip speed under all drive conditions because of limited understanding of dry clutch friction mechanisms. Accordingly, a conventional controller of the robotized manual transmission system is not designed to directly observe and use clutch torque in order to detect undesirable NVH behaviors and take corrective closed-loop actions in real-time during clutch release, slip and engagement processes.